Advantages seen with myoelectric pattern recognition vs direct control for transhumeral amputees

Among transhumeral amputees who had targeted muscle reinnervation for myoelectric prosthesis control, pattern recognition control was a viable option that showed functional advantages compared with direct control, according to researchers at the Shirley Ryan AbilityLab Center for Bionic Medicine in Chicago.

“Targeted muscle reinnervation is now a clinically accepted procedure performed around the world, and pattern recognition is commercially available through Coapt Complete Control,” Levi J. Hargrove, PhD, lead author of the study, told O&P News. “This randomized clinical trial shows that patients have better functional outcomes and prefer to use pattern recognition. A second important finding shows that patients learn to use the pattern recognition control system over the duration of the home trial. They perform better after using the system at home, whereas there is no significant improvement in control for patients using the direct control system.”

According to the researchers, the use of commercialized powered prosthetic devices is limited by conventional, direct control methods, which are based on electromyographic signals produced from a limited set of muscles. However, targeted muscle reinnervation, a nerve transfer procedure, can create additional recording sites for myoelectric prosthesis control.

To compare pattern recognition and direct control among transhumeral amputees who had targeted muscle reinnervation, the researchers recruited eight participants in a balanced, randomized cross-over study. The patients completed a 6-week to 8-week home trial using direct and pattern recognition control, with a custom prosthesis made from commercially available parts.

According to the researchers, the participants reported statistically better performance in the Southampton hand assessment procedure and the clothespin relocation task, tests that require movements along 3° of freedom. Of the eight participants, seven reportedly preferred pattern recognition control over direct control.

According to researchers, the study was the first home trial large enough to establish clinical and statistical significance in comparing the two forms of control.

“Over the past decade, significant research and development efforts have been put into the prosthetics and orthotics field,” Hargrove said. “We are now seeing the rewards of these research programs, and patients across the world are benefiting from these investments. We are now investigating even newer control approaches [that] we hope will result in further advances.” – by Jason Laday